A road upgrade programme in Belfast, which was to be largely funded by the EU, has been put on hold following the referendum.
The upgrade of the York Street interchange, used by 100,000 vehicles every day, was planned to improve air quality and traffic flow, as well as make journey times more reliable.
However 40% of the funding for the project, which was scheduled to begin autumn 2017, was to come from the EU, and the FTA has said Transport NI has written to those tendering for the work to say the project has been put on hold.
Seamus Leheny, FTA’s Northern Ireland manager, said the association’s members would be “bitterly disappointed” if the work doesn’t go ahead as planned.
He added: “Commercial vehicle operators from right across the country consistently state that the M1, M2, Westlink road corridor is the most problematic and costly for their vehicles to navigate.
“Commercial vehicle operators contribute significant revenue to the Government through fuel duty, vehicle ownership tax and road user levy so it is reasonable for them to expect a road infrastructure that supports their industry.”